LM8-Pipework and Fittings

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Richard Gibbon & Tony Simons November 2017 – version 1.0 Module BESTT LM8 Pipework & Fittings Aim This unit will give learners an understanding of Locomotive Pipework & Fittings and how to examine for wear. The learner will consider: - * Different Braking Systems * Different types of Bogies and trucks * Different types Radial Axles and boxes * Examination and reporting Learning Outcomes LO1: Smoke Box Items LO2: Smoke Box Items (2) LO3: Footplate Topics LO4: Injectors LO5: Inspection BESTT MECHANICAL MODULE LM8 PIPEWORK & MISCELLANEOUS FITTINGS INTRODUCTION Although previous modules have covered the majority of vital parts, there are important and some safety critical items that we need to sweep up so that the whole set of modules are comprehensive in their coverage of the subject of steam locomotive building, repair, inspection and maintenance. This module will attempt to cover the vital components such as pipes that link the various major sections covered by previous modules and attempts to sweep up loose ends left out in the process by trying to sub divide this expansive subject into viable and freestanding sections. HRA Guidance Document HGR 9007 relates but there are some topics not covered It might seem that module LM8 is a blend of unrelated topics, but this approach is inevitable if we are trying to cover the whole subject appropriately. We can group the various topics loosely not covered so far under two main headings. Those associated with the SMOKEBOX and those associated with the FOOTPLATE plus a few which do not fit easily with either. SMOKEBOX RELATED TOPICS STEAM PIPES BETWEEN BOILER AND CYLINDERS Although these pipes are not strictly part of the pressure vessel they need special attention during any sort of assessment or inspection. This is because any failure of these highly stressed components can be life threatening to the crew. A rupture of one of these pipes with the locomotive under load can tend to throw the fire back out through the firehole door and engulf the crew They are generally steel (sometimes copper) are subject to full boiler pressure, across a wide temperature range and because they are bent up from thick walled pipe there is generally thinning of the outside surfaces during the bending process which stretches the outer surfaces on the bend and compresses the inner surfaces. In addition the abrasive nature of the char from the fire passing the outer surface of the pipe at high speed tends to abrade the already thinned pipe wall. All of that is on top of the acidic attack from the highly corrosive atmosphere from the sulphuric acid, which is prevalent in a smokebox during and after running. Visual inspection is inadequate to get a full picture of the condition of these items and a thorough ultrasonic survey of the pipes at overhaul or heavy exam periods is essential. In addition, during erection of the locomotive after overhaul a hydraulic test to twice working pressure is recommended so that any weakening during the ensuing life of the pipes is catered for. Additionally seen in the image above, are the copper or steel pipes which feed the blower ring around the blast pipe seen coming in from the right and the brake ejector exhaust pipe seen feeding up into the chimney petticoat. These pipes too generally made of copper need to be regularly inspected and replaced if weakened for the same reasons given above. SNIFTING OR ANTI VACUUM VALVES When a steam locomotive is running, and steam is shut off by the driver closing the regulator, the pistons within cylinders continue to sweep the same volume and expel all the steam that is left in the steam pipes and the super-heater. In effect the engine becomes a vacuum pump and three disadvantageous things happen within the steam circuit Firstly the super-heater elements are emptied of any steam, which might protect them from overheating as the heat from the fire continues to heat up the elements. Secondly the vacuum created within the super-heaters and steam chests slows the locomotive down as resistance is felt in maintaining the vacuum. Thirdly the vacuum created within the cylinder block can inevitably lead to ash and cinders being drawn down the open blast pipe into the cylinder block which is clearly bad news and will lead to premature wear. In order to prevent these things happening an anti-vacuum valve or “snifting valve” as it is sometimes known is fitted to the top of the super-heater header so that as soon as the pressure in the steam pipes subsides the valve opens to atmosphere and cold air is drawn through the super-heater elements and down into the cylinders. This ensures free running, cool super-heater elements and no ingress of char from the smokebox. The valve can be seen in the photograph, sitting about a metre behind the chimney of Tornado in the photograph is shown in diagrammatic form in the drawing. The valve can often be heard shutting with a metallic clink when the locomotive starts from rest after the regulator is first opened. The description above applies to Ex LNER locomotives, Ex LMS and Ex BR Standard Locomotives had anti-vacuum valves fitted at either end of the cylinder assembly under the running board, which performed the same function apart from letting air in to cool the superheaters when coasting. BLAST PIPE JUMPER RING Whilst still on with smokeboxes we need to cover the automatic blast-pipe jumper ring which was introduced by G.J. Churchward on the GWR to avoid excessive back pressure forming at the blast orifice. In ordinary working locomotives which use part of the exhaust steam in the injectors or for other purposes need a smaller blast pipe orifice than they would otherwise have. But on the other hand when the locomotive is being pressed to work hard, the blast may easily become too fierce and the back pressure on the pistons be increased correspondingly. When the locomotive fitted with this particular type of blast pipe comes to a gradient or causes more than a pre-determined amount of steam to pass through the cylinders out up the chimney, the heavy jumper ring rises and remains up until the exhaust steam is reduced when it falls back to its original position. The rising of the “Jumper” increases the area of the blast pipe by 9 square inches thus softening the blast and reducing backpressure. It will be seen that by automatically increasing the capacity of the blast pipe as with the “jumper” top and ring, a free outlet for the exhaust is available under normal and maximum load conditions. Other railways tried adjustable blast pipe mechanisms so the size of the blast orifice can be varied by the driver according to the work that is being performed, but they are liable to get out of order through the ashes and coal dust choking up the working parts. BLAST PIPE “JIMMY” Following on from the Jumper top described above this item is related but comes from a really unusual angle. Some locomotives were poor steamers for a variety of reasons and the crew were faced with trying to keep to time when the locomotive would not perform as expected. In order to liven up the fire to make more steam the locomotive crew devised and had made this illegal device which they were able to apply to the inside of the blast-pipe nozzle. The adjustable jaws fitted down into the mouth of the blast pipe and the sharp edge of the square bar lay across the orifice. This had the disruptive effect of dividing the blast from the exhaust into two diverging flows, which thus increased the speed of the exhausting steam and caused the exhaust to completely fill the petticoat pipe and created more vacuum in the smokebox. Of course the Railway Management didn’t approve as the use of Blastpipe Jimmys increased coal consumption of the locomotive. The crews had to be careful to make sure the devices were removed before the locomotive returned to its shed. These items were kept hidden in the crew’s toolboxes and this particular one was presented to the management upon the retirement of a famous driver. It is interesting that the more sophisticated design of blast pipes developed by French and other locomotive designers echoed the method used here. Learners should research KYALA and CHAPELON’s work as well as LEMPOR. The A4’s like Mallard were fitted with Kychap (derived from the first two names together) blast arrangements, which were created to markedly improve blast pipe and smokebox performance SMOKEBOX STEAM LANCE In order to help cleaners and firemen get their locomotives ready and dispose them at the end of the day there was a fitting on the lower right hand side of the smokebox which was connected to the boiler pressure by a pipe inside the smokebox.

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